Spectrophotometers can be used to measure the intensity of light as a function of its wavelength over a spectral range of light (e.g., the spectral bandwidth of the spectrophotometer). For a spectrophotometer, important aspects of measurements include the absorption, transmittance, and reflectance of light by samples, for example, measured as a percentage or other gauge or metric. Spectrophotometers are often used to identify or determine the quality or quantity of solutions and solids based on the transmittance and reflectance characteristics of those samples.